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caddmannq · 04-02-2002, 11:55 AM

Did you do the lights/horn/brake light test?

It could be a burned solenoid.

Also, a battery can test 12 volts with no load, but not be able to deliver any amps at that voltage because of an internal crack or meltdown of the conductors.

You might have a constant drain on the battery, with the key off, too. (Actually all cars do, but it's very slight. A healthy battery should take months to drain down in a good system.)

Alternators with bad diodes can do this, plus they will only charge weakly. Also any short, a computer malfunction, interior light that does not go off (sometimes under the hood or trunk where you don't notice it) even a defective radio, can drain the battery while you sleep.

Problems in the starting/charging system also "feed" on each other. For instance: A poor cable connection will make the car hard to start. This drains the battery a bit too much. Plus it makes the alternator work harder to replace the extra drain, plus fight the resistance of the bad connection. This puts a strain on the alternator, leading to regulator & diode burnout. This further reduces charging of the battery, which increases amp draw at the next start. The high amp draw further worstens the connection, plus burns contacts in the solenoid, and brushes + windings in the starter. This causes even more amp draw, harder starting, and melts down the internal connections between cells in the battery. It doesn't have to happen in exactly that order: but it's all related as a system.

This cycle can go around and around until one componant of the system fails, and the car does not start at all.

But replacing the failed componant usually does not completely fix the problem, and another failure can occur. You must determine the health of the entire system, and find the root cause of the problems.

90% of the time, these things all point back to a loose or corroded cable as the instigator: but assume nothing. Check everything.

If your mechanic replaces the battery (or starter, or whatever), ask him if he cleaned & tightened ALL the cables (on BOTH ends!), did an alternator output test, and a starter draw test, and a battery current leakage test.

Without those, he's just guessing.

04-02-2002, 11:55 AM	#9 (permalink)
caddmannq Registered User Join Date: Oct 2001 Location: Clovis, CA Posts: 2,481	Did you do the lights/horn/brake light test? It could be a burned solenoid. Also, a battery can test 12 volts with no load, but not be able to deliver any amps at that voltage because of an internal crack or meltdown of the conductors. You might have a constant drain on the battery, with the key off, too. (Actually all cars do, but it's very slight. A healthy battery should take months to drain down in a good system.) Alternators with bad diodes can do this, plus they will only charge weakly. Also any short, a computer malfunction, interior light that does not go off (sometimes under the hood or trunk where you don't notice it) even a defective radio, can drain the battery while you sleep. Problems in the starting/charging system also "feed" on each other. For instance: A poor cable connection will make the car hard to start. This drains the battery a bit too much. Plus it makes the alternator work harder to replace the extra drain, plus fight the resistance of the bad connection. This puts a strain on the alternator, leading to regulator & diode burnout. This further reduces charging of the battery, which increases amp draw at the next start. The high amp draw further worstens the connection, plus burns contacts in the solenoid, and brushes + windings in the starter. This causes even more amp draw, harder starting, and melts down the internal connections between cells in the battery. It doesn't have to happen in exactly that order: but it's all related as a system. This cycle can go around and around until one componant of the system fails, and the car does not start at all. But replacing the failed componant usually does not completely fix the problem, and another failure can occur. You must determine the health of the entire system, and find the root cause of the problems. 90% of the time, these things all point back to a loose or corroded cable as the instigator: but assume nothing. Check everything. If your mechanic replaces the battery (or starter, or whatever), ask him if he cleaned & tightened ALL the cables (on BOTH ends!), did an alternator output test, and a starter draw test, and a battery current leakage test. Without those, he's just guessing.